The Hacienda del Sol, in Borrego Springs, CA
Dick Zerbe was the architect who designed most of the hotel's buildings. It was initially built in 1947, but most of the cool stuff was added when the second owner of the property hired Zerbe in the late 50s. At that point, the main building was remodeled and additional rooms were added.
I was told by someone at the hotel that the room numbers are original.
For more information on Borrego Springs and what it has to offer in terms of modern architecture, visit Borrego Modern.